Directional borehole operations, such as directional drilling, involve varying or controlling the direction of a downhole tool (e.g., a drill bit) in a wellbore to direct the tool towards a desired target destination. In directional drilling, for example, the direction of a drill bit is controlled to direct the bit, and the resultant wellbore, towards a desired target destination.
Various techniques have been used for adjusting the direction of a tool string in drilling a borehole. Slide drilling, for example, may be performed using a downhole motor and a bent housing to selectively change the direction in which the borehole is being drilled. Normally, the entire drill string, including the downhole motor and bent housing, is rotated from the surface, for a zero net change in direction (nominally straight drilling). The direction of drilling may be changed by using the downhole motor alone to rotate the bit while drill string rotation is halted, such that the bent housing deflects the bit in the desired direction. When the desired directional change is achieved, rotation of the string from the surface may be resumed.
Slide drilling systems may have challenges related to halting drill string rotation. For example, a non-rotating drill string is subject to buckling in the wellbore and reduced hole cleaning efficiency.
In contrast to slide drilling systems, directional drilling systems typically have an adjustable housing angle that may be dynamically controlled while drilling to effectively steer the borehole being drilled. This allows the entire drill string to continue rotating while changing the direction of the borehole. By maintaining drill string rotation, directional drilling systems overcome various deficiencies of slide drilling.
An example of a tool for controlling deflection in a directional drilling system (i.e. a rotary steerable module) typically includes a shaft that rotates with the drill string surrounded by a housing that deflects the shaft thereby pointing the bit, an internally rotatable articulated coupling of two shafts (Point the Bit), or a fully rotating or partially geo-stationary device with radial push pads/gauges. By deflecting the shaft, the direction of the downhole end of the shaft is changed to also change the direction of drilling of the drill bit.
The illustrated figures are only exemplary and are not intended to assert or imply any limitation with regard to the environment, architecture, design, or process in which different embodiments may be implemented.